Field of the Invention
The invention relates to a wireless transceiving device.
Description of Related Art
In present Wi-Fi product design, access point (AP) generally has superior radio frequency (RF) transmitting power and receiving sensitivity. However, since wireless user devices (for example, a mobile phone, a tablet personal computer (PC), a notebook, etc.) should lower the RF power to increase battery durability, most of the wireless user devices adopt a low RF transmitting power design. Moreover, in order to avoid radiation damage caused by the wireless user devices, the wireless user devices are further required to satisfy a specific absorption rate (SAR) regulation, thus the wireless user devices cannot transmit stronger RF power.
Namely, under a general usage situation, although the wireless user device can receive a Wi-Fi signal coming from the AP, the wireless user device might fail to transmit the wireless signal to the AP due to the low RF transmitting power design. Therefore, the wireless user device probably cannot successfully access the wireless network due to unstable connection with the AP. Moreover, the aforementioned situation can be more worse in a multi-path and multiple-barriers environment.
Prior art methods tend to use more antennas and multi-input multi-output (MIMO) system in the AP to solve the aforementioned problems. However, such method results in higher cost and a more complicated circuit design, as a result, the price of a high-end product cannot be afforded by a general consumer.
Minimum detectable signal (hereinafter MDS) is a specific value of minimum receivable power, furthermore, it is defined as the equivalent noise power presenting on the input to a receiver that sets the limit on the smallest signal the receiver can detect. In order to overcome MDS limitation/receiver sensitivity, some well-known technologies have been implemented, such as MRC (maximum ratio combining), STBC (space-time block coding), LDPC (low-density parity-check code), etc.
FIG. 1 is a structural diagram of a conventional AP. In FIG. 1, the AP 100 includes a RF circuit (which is also referred to as a RF circuit 110, for example, a RF integrated circuit (RFIC), though the invention is not limited thereto) and n sets (n is a positive integer) of transceiving combinations TR1-TRn. As illustrated in FIG. 1, the signal to noise ratio (SNR) can be obtained according to the proportion of the RF signal power and the noise power (for example, thermal noise power of printed circuit board and assemble (PCBA)), so as a current minimum detectable signal (MDS) is determined.
In order to improve a receiving capability, an AP in FIG. 2 is further proposed to provide a better SNR. FIG. 2 illustrates an AP with an antenna diversity design. Compared to FIG. 1, the AP 200 of FIG. 2 can be equivalent to the AP 100 which adds a diversity path 210. In order to support the functions in FIG. 2, RFIC chip supplier needs to design additional control software corresponding to the added diversity path 210. Although adding one more receiving path in the AP 200, the diversity path 210 is merely used to replace the receiver with poorer receiving performance in the transceiving combinations TR1-TRn during the operation of the AP 200, the receiving performance of the AP 200 is not greatly improved while compared to AP 100.
Moreover, a high gain antenna in various transceiving combinations TR1-TRn is also commonly used for increasing the receiving performance of the AP 100. The high gain antenna is a directional antenna with a focused, narrow radio wave beam width, and is commonly used in a base station. However, since a transmitter and a receiver in each of the transceiving combinations TR1-TRn share the same antenna, the antenna of the transmitter is limited by related regulations (for example, a federal communications commission (FCC) certification and a CE certification), therefore it is not suitable for an indoor AP with the high gain directional antenna. Moreover, an average gain or efficiency of the high gain directional antenna is only about 80%. Therefore, using the high gain antenna in each of the transceiving combinations TR1-TRn cannot effectively improve the receiving performance of the AP 100.
Furthermore, the gain of the antenna can be enhanced by implementing a beamforming technique on the antenna. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. However, since the AP cannot be directional during the receiving operation, the AP can only use the transmit beamforming. Moreover, the beamforming technique requires the RFIC chip supplier's help to design the corresponding algorithm. In addition, while using the beamforming technique, it is assumed that the RF signal has to be received first, i.e. when the AP failed to receive the RF signal from the wireless user devices due to an excessively long distance, etc., the beamforming technique cannot work. Also in this case, the MDS limitation still exists.
Most of the RFIC chip suppliers adopt a maximum ratio combining (MRC) mechanism to improve the receiving performance of the AP with MIMO structure. However, the maximum gain that can be reached by the MRC mechanism is limited by the number of the receiving paths. For example, the maximum gain that can be reached by three receiving paths is 3 times, i.e. 4.7 dB. Besides, all the above techniques rely on the support from the RFIC chip supplier, manufacturing cost of the RFICs is rather higher.
Therefore, it is an important issue for related technicians how to break the MDS limitation and to improve the AP receiving performance without increasing the manufacturing cost, such that the wireless user device may have prolonged battery durability based on a lower RF transmitting power.